This invention relates to a method of making dripless metal can nozzles and more particularly to a method of making dripless can nozzles which can be fashioned from low cost tin plate.
In metal containers, and particularly in containers for food stuffs and for hazardous materials such as fuel and poisonous substances, it is desirable to prevent drops from forming on the nozzle of the can after the can is uprighted from its pouring position. Drops that remain on the rim of the nozzle will tend to run down the outside of the nozzle and collect on the top of the can around the top rim of the can, resulting in unsanitary conditions for food cans and dangerous conditions for cans containing hazardous substances.
In non-metallic containers a dripless rim is formed by forming a sharp edge at the outward extremity of the rim to cut off the liquid flow sharply when the container is righted after pouring. In metal containers, and particularly in sheet metal containers, it is not feasible to form the terminal edge of the nozzle in a free edge because the metal is sharp and easily deformed at the rim. The sharp edge presents a danger of cuts to the user, and a deformed rim leaks because it is no longer perfectly coplanar with the cap and its seal.
Accordingly, the best dripless nozzle for a sheet metal can to date has been the use of an outward curl on the nozzle rim. The outward curl increases the strength of the rim so that it is able to resist dents and the like which would prevent a good seal with a cap. The curl is continued around so that the free end of the metal is tucked underneath the curl and therefore does not present the danger of a sharp metal edge to the user.
The curl nozzle rim is expedient because it is inexpensive and produces a rim which provides some dripless effect. However, there are several disadvantages to this type of nozzle which the art has long sought to eliminate. It is necessary to use a metal having high ductility, otherwise, when the outward curl is formed the terminal edge of the metal will split which can result in leaks. Moreover, although the dripless feature of this form of nozzle is better than other available sheet metal can nozzles, it would be desirable to improve this feature.
One approach to the prevention of splits in the rim of low ductility sheet metal can nozzles was to form an initial outward flare at the can top and then form an inside hem at the rim in preparation for forming the full bead or curl at the rim of the can nozzle. Although this technique did indeed prevent splits in the metal, it did not result in improved dripless performance.
Accordingly, the art has long looked in vain for a sheet metal can nozzle which could be formed of low cost, low ductility sheet metal and which would provide excellent dripless performance.